Medical devices may be used to treat a variety of medical conditions. Depending upon the medical condition, medical devices can be surgically implanted within, or connected externally to the patient receiving treatment. For some medical conditions, medical devices provide the best or only therapy to restore an individual to a more healthful condition and a fuller life. Examples of medical devices that deliver a therapy include electrical stimulators and therapeutic agent delivery devices.
If one or more components of a medical device are damaged or otherwise fail to operate as intended, the medical device may deliver ineffective or otherwise inappropriate therapy to the patient. In some cases, if a malfunctioning device is mistaken for a therapy that is truly ineffective for the particular patient, a therapy might be unnecessarily discontinued or have corrective action postponed. To help detect issues with a medical device or its components, integrity diagnostics may be performed.
Medical devices that deliver electrical stimulation do so via electrodes located on, or implanted within the patient. The electrodes may be at a target location for receipt of the stimulation in order to provide the desired therapeutic effect. The medical device containing the stimulation generator may be at a different, more convenient location given its size or shape, e.g., outside of the patient, or implanted within the patient at a location capable of accommodating the medical device. The medical device may be coupled to the electrodes by one or more leads, each lead containing one or more conductors.
Some medical devices perform integrity diagnostics to test the condition one or more of the electrodes, leads, or stimulation generator. One example of such an integrity test is to check the impedance between pairs of electrodes. This lead integrity test can be performed on leads and electrodes to verify that the leads and electrodes are functioning properly, and are positioned correctly. During testing, the medical device delivers a signal having a known electrical characteristic, e.g., current or amplitude, between two or more electrodes. Another electrical characteristic of the signal may be measured, and the impedance may be computed between electrodes using known fundamental relationships. The measured impedance value can give a medical professional or other user information relating to whether the electrodes involved in the test, as well as the conductors that coupled to those electrodes, are operating properly.
Medical devices that deliver a drug or other therapeutic substance may do so via a catheter, or the like, that is at least partially implanted within the patient. The catheter conveys the therapeutic substance from a pump within the medical device to a target location within the patient. A partial or complete blockage of the catheter could prevent the therapeutic substance from reaching the delivery site in the patient or, in the case of a partial obstruction, could prevent an adequate supply of the therapeutic substance from reaching the delivery site in the patient. A leak (e.g., due to a tear or cut), small or large, can also prevent the therapeutic substance from reaching the delivery site in the patient. A leak can result in a double problem. In addition to the lack of therapeutic substance supplied to the delivery site of the patient, the therapeutic substance could be dispersed elsewhere in the body of the patient, which may create further issues.
Some medical devices perform integrity diagnostics to test the condition one or more of the catheters or pumps. As an example, a catheter integrity test may measure the flow or pressure within the lumen of a catheter to detect tears or occlusions in the catheter. An abnormal increase in pressure within a lumen of a catheter may indicate an occlusion. Whereas, a decrease in pressure may indicate a tear. A decrease in flow may indicate either a tear or an occlusion. The measured flow and/or pressure values can give a medical professional or other user information relating to whether the catheter involved in the test is properly delivering a therapeutic substances to a target therapy delivery site.